Well seeing Dave play I guess xbows are fine.. although still not my cup of tea. He does kill a lot in melee too though, not sure what the score would be if that is subtracted.
The reason why I don't want xbows stronger is Strategus. Ranged is going to be very strong there as usual.
I say leave it the way it is now, but throwing needs to be checked a bit. I don't want to repeat myself as I think we are in agreement for the most part!
But to answer your question, even with primary crossbow builds, the melee weapon will usually end up being either 1/3 or 1/2 of your kills. This isn't the case in siege really, but in battle it totally is for me at least. Depending on the bow you use, having just a crossbow won't work nearly as well as a pure throwing build like FF_George_Washington or Templar_Damugger